Construction on the world's largest hydropower project undergoing at the Three Gorges in central China's Hubei Province yielded some negative effects on environment, but the scale is under control, said a senior company executive with the China Yangtze River Three Gorges Project Development Corporation on Friday.

Cao Guangjing, deputy general manager of the project undertaker said the company has comprehensive measures to deal with various environmental problems concerning the project.

After years of researches, scientists studying on the project's environmental issues believed that the hydropower project would affect water lives, water quality, cause silt accumulation and maybe slightly modify local climate through years in the dam's surrounding areas.

"The negative effects of industrial sewage and dust produced in the project's construction process on environment is under control," Cao said.

With its first pickaxe fell in 1994, the mammoth Three Gorges project will have its major structure, the dam's 185-meter-high main section, completed on Saturday, which involves placement of approximately 16 million cubic meters.

Environmental protection has been one of the top concerns of the Three Gorges project, according to Sun Zhiyu, head of the environmental protection section of the project development corporation.

He said a great deal of sewage was produced in the concrete manufacturing for the project. Only after it had been decontaminated, could it be discharged, he stressed, adding that half of the sewage has been processed.

Ice bricks are being added to concrete mixers so as to keep the temperature at not higher than 14 degrees Celsius. This move has objectively reduced dust production.

Li Yong'an, general manager of the China Yangtze River Three Gorges Project Development Corporation, said the project has pooled the state-of-the-art construction equipment and techniques.The operation of large machines is also conducive to mitigating the project's negative effects on environment, Li added.

When the Three Gorges reservoir start to further store water, more than 1,500 enterprises will be submerged, most of which are small ones causing serious pollution and incurring big losses. To this end, the Chinese Government has decided to shut down 1,000 out of them. Meanwhile, sewage treatment and garbage disposal plants are being built at a combined cost of 40 billion yuan (5 billion U.S. dollars), so as to protect ecosystem and water quality in the dam area.

Besides, the project development corporation has spent 10 million yuan (1.3 million U.S.dollars) annually in three consecutive years to skim and collect floating garbage from upstream of the dam. According to the latest evaluation made by the Three Gorges Water Environment Monitoring Center, the water at the dam area is up to the state criteria for drinking water.

Moreover, China exerted endeavors to protect natural forests and plant trees at the dam area and in the upper reaches of the Yangtze River over the recent 10 years. The result is continuous reduction of silt in the river.

According to monitoring data from the Yangtze River Water Resources Committee, silting at the dam has, since the Three Gorges reservoir began to store water, kept decreasing by 100 million tons annually.

The 180-billion-yuan (22.5 billion U.S.dollars) Three Gorges Project, including a 185-meter-high dam and 26 generators on both banks of the Yangtze River, is being built in three phases on the middle reach of China's longest river. It is scheduled for completion in 2009 and by then, it will be able to generate 84.7 billion kwh of electricity a year.

The Three Gorges, which consist of Qutang, Wuxia and Xiling Gorges, extend for about 200 km on the upper and middle reaches of the Yangtze. They have become a popular world-class tourist destination noted for beautiful natural landscapes and a great number of historical and cultural relics.

An ancient legend says the Three Gorges were cut by Dayu, a legendary flood control hero, when he was combating the floodwater.This section of the Yangtze has a narrow river course that abounds in hydroelectric resources.

Apart from generating electricity, the Three Gorges Project is also designed to harness flooding and benefit shipping.